1. Field of the Invention
The present invention relates to a resin-sealed type semiconductor device, and especially to a one-side resin-sealed type semiconductor device in which a surface of a lead frame on which a semiconductor element is mounted is sealed with a resin and a lead frame used therefor.
2. Description of Related Art
Resin-sealed type semiconductor devices each provided with a lead frame for electrically connecting electrodes of the semiconductor to an outer wiring and the like are widely used. In such a semiconductor device, a lead frame generally comprises a supporting portion for mounting a semiconductor element thereon, hanging lead portions for supporting the supporting portion, and lead terminal portions for connecting metal wires thereto. A lead frame used in the process of fabricating semiconductors includes a plurality of unit regions corresponding to a plurality of semiconductor devices so that the plurality of semiconductor devices can be fabricated at the same time. One unit region has a substantially rectangular shape. Each of the hanging lead portions extends inwardly from a corner portion of this rectangle, and in many cases, the lead terminal portions extend inwardly from side parts of the unit region.
FIG. 5 is an enlarged schematic pan view showing a part in the vicinity of a corner of a unit region.
In the central part of the substantially rectangular unit region (in the direction of arrow G), a supporting portion 51 is disposed. A hanging lead portion 52 extends from the supporting portion 51 toward the corner portion. In the side parts of the unit region, substantially rectangular lead terminal portions 53 are provided. Base end portions of the lead terminal portions 53 are connected to a peripheral frame part 50. The longitudinal direction of the hanging lead portion 52 and the longitudinal direction of the lead terminal portion 53 makes an angle of substantially 45°.
In a lead frame, a plurality of unit regions each having such a structure are arranged and connected to the frame part 50. In the process of fabricating semiconductor devices, a lead frame is sealed with a sealing resin in such a manner that the bottom surface of the lead terminal portion 53 is exposed. Thereafter, each unit of lead frame is cut along a cutting line M shown in broken line, and the cut end face is substantially in the same plane with the side surface of the sealing resin.
In order to obtain a small-sized semiconductor device, it is preferable that the length of the lead terminal portion 53 is as short as possible. However, since the lead terminal portion 53 functions as a lead for connection with outer wiring substrate, the lead terminal portion 53 needs to have a length (area) more than a predetermined length (area). From these reasons, the lead terminal portion 53 is formed to have a predetermined necessary minimum length L1.
The minimum distance between the hanging lead portion 53 and the lead terminal portion 53A adjacent to the hanging lead portion 53 must be large enough to ensure insulating reliability between them. However, in order to obtain a small-sized semiconductor device, it is preferable that the minimum distance between them is small. From these reasons, the minimum distance between them is designed to be a predetermined necessary minimum distance L2.
However, since the predetermined length L1 and the predetermine distance L2 are required to be secured, miniaturization of mounting area of a semiconductor device is limited.